Live Thumbnail Image Generation

ABSTRACT

Various arrangements for generating thumbnail images for video content as the video content is being received are presented. A television receiver may first receive video content. A thumbnail generation process may be woken from a sleep state based on a predefined time period elapsing. The received video content may be monitored for a next-received I-frame. A thumbnail image may be created from the I-frame and may be mapped to a timestamp. The thumbnail generation process may then be caused to enter the sleep state for the predefined time period.

BACKGROUND

Thumbnail images can be a useful visual reference to a user navigatingthrough video content. By viewing thumbnail images, a user may be ableto determine if the user needs to navigate forward, back, or is at adesired location within the video content. Generation of thumbnailimages can be a processing-intensive task, which could negatively affectother tasks that require processing. If a user may view video contentsoon after it is received, it may be desirable to have thumbnail imagescreated and ready as soon as possible for use in navigation to allow theuser to navigate efficiently and effectively through the video content.

SUMMARY

Various arrangements for generating thumbnail images for video contentnavigation are presented. In some embodiments, a method is presented. Inother embodiments, a television receiver or processor-readable mediummay be presented. A television receiver may receive video content. Whilethe video content is being received, various functions may be performed:A thumbnail generation process may be woken or activated from a sleepstate. The received video content may be monitored for an I-frame. Athumbnail image may be created that is mapped to a timestamp. Thethumbnail generation process may cause the thumbnail image mapped to thetimestamp to be stored. In response to storing the thumbnail image, thethumbnail generation process may enter the sleep state.

Embodiments of such arrangements may include one or more of thefollowing features: The thumbnail generation process may be woken fromthe sleep state based on determining a predefined time period hasexpired. The thumbnail generation process may be woken from the sleepstate based on a current processing load of the one or more processors.Receiving the video content may include: decrypting a control message toobtain a descrambling key; receiving scrambled video content; anddescrambling the scrambled video content using the descrambling key,wherein the thumbnail image is created after the scrambled video contentis descrambled. After descrambling the scrambled video content using thedescrambling key and creating the thumbnail image, the video content maybe encrypted, wherein the thumbnail is created before the descrambledvideo content is encrypted. The encrypted video content may be stored toa processor-readable storage medium of the television receiver. Thereceived video content may be stored to a time shift buffer stored on anon-transitory computer-readable medium. During the sleep state, thethumbnail generation process may only monitors whether the predefinedtime period has elapsed since a previous thumbnail was generated.Storing the thumbnail image mapped to the timestamp may include: a firstfile being created that stores a plurality of thumbnail images, theplurality of thumbnail images comprising the thumbnail image; and asecond file being created that links each of the plurality of thumbnailimages with a timestamp of a plurality of timestamps. While the videocontent is being received, a video content navigation interface may beoutput for presentation, wherein the video content navigation interfacecomprises: a scrub bar; and the thumbnail image, wherein a time mappedto the timestamp of the thumbnail image is currently selected.Outputting the video content navigation interface may include: receivinguser input selecting a location on the scrub bar; and presenting asecond thumbnail image that is mapped to a timestamp corresponding tothe location on the scrub bar. The thumbnail image may be a reducedresolution version of the I-frame.

BRIEF DESCRIPTION OF THE DRAWINGS

A further understanding of the nature and advantages of variousembodiments may be realized by reference to the following figures. Inthe appended figures, similar components or features may have the samereference label. Further, various components of the same type may bedistinguished by following the reference label by a dash and a secondlabel that distinguishes among the similar components. If only the firstreference label is used in the specification, the description isapplicable to any one of the similar components having the same firstreference label irrespective of the second reference label.

FIG. 1 illustrates an embodiment of a system that generates livethumbnails.

FIG. 2 illustrates an embodiment of a television receiver that mayinclude the system of FIG. 1 and may generate live thumbnails.

FIG. 3 illustrates an embodiment of an interface that allows forthumbnail-based navigation.

FIG. 4 illustrates an embodiment of a method for generating livethumbnails.

FIG. 5 illustrates an embodiment of a method for using generated livethumbnails for navigation in video content.

DETAILED DESCRIPTION

Generation of thumbnail images (referred to as “thumbnails” for short)as video content is received by a television receiver may have severaladvantages. First, by generating the thumbnails as content is received,the thumbnails may become available for use for navigating through videocontent sooner than if the thumbnails were created as part of a batchprocess after the video content has been fully received. Second, videocontent may be received in an encrypted or scrambled format andsubsequently decrypted or descrambled for output, storage, or furtherprocessing. When such content is stored locally, the video content maybe re-encrypted or re-scrambled. By creating thumbnails as the videocontent is received and initially descrambled or decrypted, a laterdescrambling or decryption step solely or primarily for the purpose ofthumbnail generation may be avoided, thereby decreasing the total amountof processing needing to be performed.

A possible disadvantage of generating thumbnails can be the consumptionof processing resources. Therefore, if a processing system is being usedfor multiple tasks, generation of one or more thumbnail images maynegatively impact the processing resources available for other tasks.For instance, if a user is viewing content as it is being received orfrom a time-shift buffer, generation of thumbnails may negatively impactthe quality of audio and/or video output for presentation to the user orthe ability of the device to perform real-time descrambling, decryption,and/or storage. In order to avoid such a disadvantage, a sleep processmay be incorporated as part of the thumbnail generation process suchthat the thumbnail generation process is only active for a relativelyshort period of time when a predefined time period has expired. Once athumbnail is generated and stored, the thumbnail generation process mayreturn to a sleep state for the predefined time period. Further, thethumbnails and associated metadata (e.g., timestamps) may only bewritten to a hard drive or solid-state drive (or other long-term storagedevice) after a certain number of thumbnails have been generated or someother trigger event has occurred. As such, the number of writeoperations to the hard drive or solid-state drive may be decreased.

In some embodiments, one or more additional actions may be taken toreduce the processing load of thumbnail generation as live content isreceived. In some embodiments, the amount of time between whenthumbnails are generated may be dynamically varied based on theprocessing load on the one or more processors of the televisionreceiver. Therefore, if the one or more processors are currently beingsignificantly utilized, the amount of time between generation ofthumbnails may be increased (to decrease the amount of processing loaddue to thumbnail generation). Additionally or alternatively, thethumbnail interval may be adjusted based on the type of display thatwill be used to output the content for presentation. For example, on asmall display, having fewer thumbnails (which may be created using alower resolution) may be sufficient for navigation. A smaller number ofthumbnails may be sufficient due to the size of the scrub bar (due tothe size of the display) and the inability to do highly precisemovements with a finger on a small scrub bar. Therefore, the size and/orresolution of a display that will be used for output may be taken intoaccount to determine the amount of time and/or resolution forthumbnails. Additionally or alternatively, thumbnail creation may beoffloaded to a cloud-based server. An I-frame may be sent to thecloud-based server. The cloud-based server will do the frame decoding,resizing, then re-encode as a JPEG image (or other format). Thisarrangement may increase network traffic, but may decrease the amount ofprocessing performed locally by the one or more processors of thetelevision receiver. Cloud-based thumbnail generation may be triggeredby the one or more processors experiencing at least a threshold level ofprocessing load.

Further detail regarding the embodiments is provided in relation to thefigures. FIG. 1 illustrates an embodiment of a system 100 that generateslive thumbnails. “Live” refers to the concept that the thumbnails aregenerated as the video content is received rather than as part of abatch process performed at a later time. When system 100 receives videocontent and is triggered to generate a thumbnail, the thumbnail may begenerated and ready for use in presentation as part of a navigationalinterface within a short time, such as 0.25 s-5 s. System 100 may beincorporated as part of a television receiver. Such a televisionreceiver may be in the form of a set top box (STB) component that isintegrated as part of a television, or a computerized device that isconfigured to present video content. For instance, a computerized devicesuch as a digital media player, smartphone, tablet computer, or gamingdevice may have an application installed on it that allows for videocontent to be received, recorded, and/or output for presentation (eitherdirectly via a display of the computerized device or via an externaldevice (e.g., television)).

System 100 may include: video content receiver 110; decoder engine 120;thumbnail generation engine 130; thumbnail and metadata buffer 140;thumbnail datastore 142; metadata datastore 144; encoder engine 150;content datastore 160; output interface 170; and navigation interfacegenerator 180.

Video content receiver 110 may receive a stream of video from a source,such as a streaming video provider. The streaming video received may bea television channel, or some other form of streaming media, such as astreamed television program, movie, or other form of content. In someembodiments, streaming audio may accompany the streaming video. Videocontent receiver 110 may receive streaming video via a dedicated mediadistribution network, such as a satellite-based communication network.In some embodiments, video content receiver 110 may receive videocontent via some other form of network, such as an IP-based network,such as the Internet. Therefore, video content receiver 110 may includeone or more network interfaces, such as a Wi-Fi network interface. Videocontent receiver 110 may also include specialized hardware to allowvideo content receiver 110 to receive video content from a specializedcontent distribution network. For example, video content receiver 110may include one or more tuners configured to receive content broadcastvia satellite. In other embodiments, video content receiver 110 may beconfigured to receive content via a cable network or over the air (OTA).

Decoder engine 120 may generally refer to software, firmware, and/orhardware that can decode, decrypt, and/or descramble received videocontent. Decoder engine 120 may perform multiple functions, such asdecrypting an encrypted message (e.g., an entitlement control message)to obtain a key (e.g., control word) that is used to descramble videocontent. Further detail regarding such an arrangement is provided inrelation to FIG. 2. In other embodiments, the video content may not bescrambled or encrypted. Scrambling generally refers to a “light” form ofencryption, which can be converted into an unscrambled version if thecorrect descrambling key is available with a minimal amount ofprocessing resources. Encryption may be understood to be much “heavier”in that a significantly greater amount of processing may be required todecrypt the encrypted message using a correct encryption key. Encrypteddata is typically more secure than scrambled data. Decoder engine 120may output decoded video content for storage to encoder engine 150,content datastore 160, or output interface 170.

Content datastore 160 may be a non-transitory processor readable medium,such as memory, a hard drive, or a solid state drive to which videocontent may be stored for a period of time. In some embodiments, encoderengine 150 may scramble and/or encrypt the descrambled and/or decrypteddata received from decoder engine 120. Encoder engine 150 may encryptand/or scramble data using one or more keys for local storage on contentdatastore 160 such that video content is not stored unprotected. Such anarrangement may help prevent theft of copyrighted materials. If the useris viewing the video content live, decoder engine 120 may output thedecrypted and/or descrambled video content to output interface 170.Output interface 170 may output the video content via a display device,such as a display screen. This display device may be incorporated aspart of the same device as system 100 or may be external from system100. For instance, system 100 may be incorporated as part of a devicethat is connected with a television or other form of display.

Thumbnail generation engine 130 may represent software or firmware thatis executed using one or more processors. Thumbnail generation engine130 may operate in at least two modes. A first mode may be in activemode, during which thumbnail generation engine 130 is activelygenerating a thumbnail image. A second mode may be a sleep mode, duringwhich thumbnail generation engine 130 is disabled and not using anyprocessing resources besides, possibly, keeping track of an amount oftime that has elapsed since the previous thumbnail was generated incomparing this amount of time with a predefined time period. Thumbnailgeneration engine 130 may, when active, monitor for a next occurringframe that is output by decoder engine 120 or otherwise received byvideo content receiver 110. The frame monitored for may be an I-frame.An I-frame may be a type of frame used in MPEG (or, more generally,video) encoding that includes all of the data necessary to render orcreate a visual image without any additional information. Other forms offrames (e.g., P-frames, B-frames) may be incremental and may rely onreferencing a previous or future I-frame. Thumbnail generation engine130 may use such I-frame to create a reduced resolution image of theI-frame. Such a reduced resolution image may be appropriate forpresentation in a smaller format.

When thumbnail generation engine 130 has created a thumbnail image, atimestamp that corresponds to the time at which the thumbnail wascreated from the received video content may be generated. This timestampand thumbnail image may be temporarily stored by thumbnail and metadatabuffer 140. Thumbnail and metadata buffer 140 may use random accessmemory or some other form of processor readable and writable memory totemporarily store the thumbnail image and the associated metadata.Occasionally, data from thumbnail and metadata buffer 140 may be writtento thumbnail datastore 142 and metadata datastore 144. For instance,after 30 minutes of thumbnails have been captured or a particular pieceof video content has ended, thumbnails and metadata from thumbnail andmetadata buffer 140 may be written to thumbnail datastore 142 andmetadata datastore 144. Thumbnail datastore 142 and metadata datastore144 may be stored to a more permanent form of processor readablenon-transitory storage medium. For example, a hard drive or solid statedrive may be used to store thumbnail datastore 142 and metadatadatastore 144. By temporarily storing thumbnails and metadata tothumbnail and metadata buffer 140, the number of writes to thumbnaildatastore 142 and metadata datastore 144 may be decreased. In someembodiments, thumbnail and metadata buffer 140 may not be present andthumbnail generation engine 130 may write thumbnails and metadatadirectly to thumbnail datastore 142 and metadata datastore 144.

After thumbnail generation engine 130 has generated a thumbnail and linkto a particular timestamp with the thumbnail, thumbnail generationengine 130 may enter the sleep mode. While in the sleep mode, the amountof processing being required by thumbnail generation engine 130 may bevery low. While in the sleep mode, thumbnail generation engine 130 maymonitor an amount of time that has elapsed since the previous thumbnailwas generated and periodically or occasionally compare this amount oftime with a predetermined time threshold. When the amount of time meetsor exceeds the predetermined time threshold, thumbnail generation engine130 may transition to the active mode.

Thumbnail datastore 142 may include one or more thumbnail storage files.Each thumbnail storage file may include multiple thumbnails. Eachthumbnail within thumbnail datastore 142 may be mapped to a uniqueidentifier (that is unique at least within the particular file).Metadata datastore 144 may include one or more metadata storage files.Each metadata storage file may include a list, table, or database oftimestamps, with each timestamp being linked with a unique identifier.Therefore, for a particular time, navigation interface generator 180 mayquery metadata datastore 144 to retrieve a particular identifier. Theidentifier may then be used to obtain the corresponding thumbnail fromthumbnail datastore 142.

Navigation interface generator 180 may be used to generate a navigationinterface to allow a user to move forward or backward within videocontent being output for presentation. The navigation interface mayinclude a scrub bar that allows a user to see what content is currentlyavailable for playback. When a user selects a different portion of thevideo content, a thumbnail may be presented to visually represent to theuser the currently selected position within the video content. Thethumbnail may be selected based on the timestamp associated with thethumbnail being closest (or the next earlier timestamp or the next latertimestamp) to the times selected on the scrub bar. Further detailregarding such an interface is provided in relation to FIG. 3.Navigation interface generator 180 may be performed using one or moreprocessors. Therefore, navigation interface generator 180 may beperformed by the same one or more processors that are being used toperform thumbnail generation engine 130.

FIG. 2 illustrates an embodiment of a television receiver 200.Television receiver 200 represents a type of device that may incorporatecomponents of and functionality of system 100 of FIG. 1. Televisionreceiver 200 may be in the form of a separate device configured to beconnected with a display device, such as a television. Embodiments oftelevision receiver 200 can include set top boxes (STBs). As previouslynoted, in addition to being in the form of an STB, a television receivermay be incorporated as part of another device, such as a television orother form of display device. For example, a television may have anintegrated television receiver (which does not involve an external STBbeing coupled with the television).

Television receiver 200 may be in the form of an STB that outputs videoand/or audio to a display device, such as a television. Televisionreceiver 200 may be incorporated as part of a television. Televisionreceiver 200 may include: processors 210 (which may include controlprocessor 210-1, tuning management processor 210-2, and possiblyadditional processors), tuners 215, network interface 220,non-transitory computer-readable storage medium 225, time-shift buffer230, television interface 235, networking information table (NIT) 240,digital video recorder (DVR) database 245 (which may includeprovider-managed television programming storage and/or user-definedtelevision programming), thumbnail datastore 142, metadata datastore144, user input device 250, decryption processing component 260 (whichcan be in the form of a removable or non-removable smartcard), and/ordescrambling engine 265. In other embodiments of television receiver200, fewer or greater numbers of components may be present. It should beunderstood that the various components of television receiver 200 may beimplemented using hardware, firmware, software, and/or some combinationthereof. Functionality of components may be combined; for example,functions of descrambling engine 265 may be performed by tuningmanagement processor 210-2. Further, functionality of components may bespread among additional components; for example, PID (packet identifier)filters 255 may be handled by separate hardware from program managementtable 257.

Processors 210 may include one or more specialized and/orgeneral-purpose processors configured to perform processes such astuning to a particular channel, and/or receiving and processing inputfrom a user. For example, processors 210 may include one or moreprocessors dedicated to decoding video signals from a particular format,such as MPEG, for output and display on a television and for performingdecryption. It should be understood that the functions performed byvarious modules of FIG. 2 may be performed using one or more processors.As such, for example, functions of descrambling engine 265 may beperformed by control processor 210-1.

Control processor 210-1 may communicate with tuning management processor210-2. Control processor 210-1 may control the recording of televisionchannels based on timers stored in DVR database 245. Control processor210-1 may also provide commands to tuning management processor 210-2when recording of a television channel is to cease. In addition toproviding commands relating to the recording of television channels,control processor 210-1 may provide commands to tuning managementprocessor 210-2 that indicate television channels to be output todecoder module 233 for output to a display device. Control processor210-1 may also communicate with network interface 220 and user inputdevice 250. Control processor 210-1 may handle incoming data fromnetwork interface 220 and user input device 250. Additionally, controlprocessor 210-1 may be configured to output data via network interface220. Control processor 210-1 may execute a process, thread, or task toperform the functions of thumbnail generation engine 130 as detailed inrelation to FIG. 1.

Tuners 215 may include one or more tuners used to tune to transpondersthat include broadcasts of one or more television channels. In theillustrated embodiment of television receiver 200, three tuners arepresent (tuner 215-1, tuner 215-2, and tuner 215-3). In otherembodiments, two or more than three tuners may be present, such as four,six, or eight tuners. Each tuner contained in tuners 215 may be capableof receiving and processing a single transponder stream from a satellitetransponder at a given time. As such, a single tuner may tune to asingle transponder stream at a given time. If tuners 215 includemultiple tuners, one tuner may be used to tune to a television channelon a first transponder stream for display using a television, whileanother tuner may be used to tune to a television channel on a secondtransponder for recording and viewing at some other time. If multipletelevision channels transmitted on the same transponder stream aredesired, a single tuner of tuners 215 may be used to receive the signalcontaining the multiple television channels for presentation and/orrecording. Tuners 215 may receive commands from tuning managementprocessor 210-2. Such commands may instruct tuners 215 which frequenciesor transponder streams to tune.

Network interface 220 may be used to communicate via an alternatecommunication channel with a television service provider, if suchcommunication channel is available. The primary communication channelmay be via satellite (which may be unidirectional to television receiver200) and the alternate communication channel (which may bebidirectional) may be via a network, such as the Internet. Thiscommunication may be bidirectional: data may be transmitted fromtelevision receiver 200 to a television service provider system and fromthe television service provider system to television receiver 200.Network interface 220 may be configured to communicate via one or morenetworks, such as the Internet, to communicate with a television serviceprovider system. Information may be transmitted and/or received vianetwork interface 220. For instance, instructions (e.g., regardingsubscription portability, recording instructions, confirmation settings)from a television service provider may also be received via networkinterface 220, if connected with the Internet. Network interface 220 maybe used to provide a confirmation to a television service provider thatinstructions received from the television service provider have indeedbeen executed.

Storage medium(s) 225 may represent one or more non-transitorycomputer-readable storage mediums. Storage medium 225 may include memoryand/or a hard drive. Storage medium 225 may be used to store informationreceived from one or more satellites and/or information received vianetwork interface 220. Storage medium 225 may store information relatedto time-shift buffer 230, thumbnail datastore 142, metadata datastore144, thumbnail and metadata buffer 140, and/or DVR database 245.Recorded television programs, which were recorded based on a provider-or user-defined timer may be stored using storage medium 225 as part ofDVR database 245. Storage medium 225 may be partitioned or otherwisedivided (such as into folders) such that predefined amounts of storagemedium 225 are devoted to storage of television programs recorded due touser-defined timers and stored television programs recorded due toprovider-defined timers.

The network information table (NIT) 240 may store information used bytelevision receiver 200 to access various television channels. NIT 240may be stored locally by a processor, such as tuning managementprocessor 210-2 and/or by storage medium 225. Information used topopulate NIT 240 may be received via satellite (or cable) through tuners215 and/or may be received via network interface 220 from the televisionservice provider. As such, information present in NIT 240 may beperiodically updated. In some embodiments, NIT 240 may be locally-storedby television receiver 200 using storage medium 225. Generally, NIT 240may store information about a service provider network, such as asatellite-based service provider network. Information that may bepresent in NIT 240 may include: television channel numbers, satelliteidentifiers (which may be used to ensure different satellites are tunedto for reception of timing signals), frequency identifiers and/ortransponder identifiers for various television channels. In someembodiments, NIT 240 may contain additional data or additional tablesmay be stored by the television receiver. For example, while specificaudio PIDs and video PIDs may not be present in NIT 240, a channelidentifier may be present within NIT 240 which may be used to look upthe audio PIDs and video PIDs in another table, such as a program maptable (PMT). In some embodiments, a PID associated with the data for thePMT is indicated in a separate table, program association table (PAT),which is not illustrated in FIG. 2. A PAT may be stored by thetelevision receiver in a similar manner to the NIT. For example, a PMTmay store information on audio PIDs, and/or video PIDs. A PMT storesdata on ECM (entitlement control message) PIDs for television channelsthat are transmitted on a transponder frequency. If, for a firsttelevision channel, multiple television channels are to be tuned to, NIT240 and/or PMT 257 may indicate a second television channel that is tobe tuned to when a first channel is tuned to.

Based on information in the NIT, it may be possible to determine theproper satellite and transponder to which to tune for a particulartelevision channel. In some embodiments, the NIT may list a particularfrequency to which to tune for a particular television channel. Oncetuned to the proper satellite/transponder/frequency, the PMT PID may beused to retrieve a program management table that indicates the PIDs foraudio and video streams of television channels transmitted by thattransponder.

Decoder module 233 may serve to convert encoded video and audio into aformat suitable for output to a display device. For instance, decodermodule 233 may receive MPEG video and audio from storage medium 225 ordescrambling engine 265 to be output to a television. MPEG video andaudio from storage medium 225 may have been recorded to DVR database 245as part of a previously-recorded television program. Decoder module 233may convert the MPEG video and audio into a format appropriate to bedisplayed by a television or other form of display device and audio intoa format appropriate to be output from speakers, respectively. Decodermodule 233 may have the ability to convert a finite number of televisionchannel streams received from storage medium 225 or descrambling engine265 simultaneously. For instance, each of decoders 234 within decodermodule 233 may be able to only decode a single television channel at atime. While decoder module 233 is illustrated as having three decoders234 (decoder 234-1, decoder 234-2, and decoder 234-3), in otherembodiments, a greater or fewer number of decoders may be present intelevision receiver 200. A decoder may be able to only decode a singlehigh definition television program at a time.

Television interface 235 may serve to output a signal to a television(or another form of display device) in a proper format for display ofvideo and playback of audio. As such, television interface 235 mayoutput one or more television channels or stored television programmingfrom storage medium 225 (e.g., television programs from DVR database245) to a television or other form of display device for presentation.

Digital Video Recorder (DVR) functionality may permit a televisionchannel to be recorded for a period of time. DVR functionality oftelevision receiver 200 may be managed by control processor 210-1.Control processor 210-1 may coordinate the television channel, starttime, and stop time of when recording of a television channel is tooccur. DVR database 245 may store information related to the recordingof television channels. DVR database 245 may store timers that are usedby control processor 210-1 to determine when a television channel shouldbe tuned to and its programs recorded to DVR database 245 of storagemedium 225. In some embodiments, a limited amount of storage medium 225may be devoted to DVR database 245. Timers may be set by the televisionservice provider and/or one or more users of television receiver 200.

DVR database 245 may also be used to record recordings of serviceprovider-defined television channels. For each day, an array of filesmay be created. For example, based on provider-defined timers, a filemay be created for each recorded television channel for a day. Forexample, if four television channels are recorded from 6-10 PM on agiven day, four files may be created (one for each television channel).Within each file, one or more television programs may be present. Theservice provider may define the television channels, the dates, and thetime periods for which the television channels are recorded for theprovider-defined timers. The provider-defined timers may be transmittedto television receiver 200 via the television provider's network. Forexample, in a satellite-based television service provider system, datanecessary to create the provider-defined timers at television receiver200 may be received via satellite.

As an example of DVR functionality of television receiver 200 being usedto record based on provider-defined timers, a television serviceprovider may configure television receiver 200 to record televisionprogramming on multiple, predefined television channels for a predefinedperiod of time, on predefined dates. For instance, a television serviceprovider may configure television receiver 200 such that televisionprogramming may be recorded from 7 to 10 PM on NBC, ABC, CBS, and FOX oneach weeknight and from 6 to 10 PM on each weekend night on the samechannels. These channels may be transmitted as part of a singletransponder stream such that only a single tuner needs to be used toreceive the television channels. Packets for such television channelsmay be interspersed and may be received and recorded to a file. If atelevision program is selected for recording by a user and is alsospecified for recording by the television service provider, the userselection may serve as an indication to save the television program foran extended time (beyond the time which the predefined recording wouldotherwise be saved). Television programming recorded based onprovider-defined timers may be stored to a portion of storage medium 225for provider-managed television programming storage.

DVR database 245 may be used to record entire television programs.Time-shift buffer 230 may be used to temporarily record video contentthat is being output for presentation while being received via tuners215 (or network interface 220). A user may begin viewing televisionprogramming “live,” but may elect to “pause” the content. While“paused,” the content may be recorded to time-shift buffer 230. The usermay then navigate forward and backward through the recorded portion ofthe content. The user may eventually catch back up the live broadcastand the time-shift buffer 230 may cease to be recorded. In otherembodiments, time-shift buffer 230 may continue to be recorded to enablerewinding through the received content.

User input device 250 may include a remote control (physically separatefrom television receiver 200) and/or one or more buttons on televisionreceiver 200 that allow a user to interact with television receiver 200.User input device 250 may be used to select a television channel forviewing, and/or program a timer stored to DVR database 245, wherein thetimer is used to control the DVR functionality of control processor210-1. In some embodiments, it may be possible to load some or all ofpreferences to a remote control. As such, the remote control can serveas a backup storage device for the preferences.

Referring back to tuners 215, television channels received via satellite(or cable) may contain at least some scrambled data. Packets of audioand video may be scrambled to prevent unauthorized users (e.g.,nonsubscribers) from receiving television programming without paying thetelevision service provider. When a tuner of tuners 215 is receivingdata from a particular transponder of a satellite, the transponderstream may be a series of data packets corresponding to multipletelevision channels. Each data packet may contain a packet identifier(PID), which, in combination with NIT 240 and/or PMT 257, can bedetermined to be associated with a particular television channel.Particular data packets, referred to as entitlement control messages(ECMs), may be periodically transmitted. ECMs may be associated withanother PID and may be encrypted; television receiver 200 may usedecryption engine 261 of decryption processing component 260 to decryptECMs. Decryption of an ECM may only be possible if the user hasauthorization to access the particular television channel associatedwith the ECM. When an ECM is determined to correspond to a televisionchannel being stored and/or displayed, the ECM may be provided todecryption processing component 260 for decryption.

When decryption processing component 260 receives an encrypted ECM,decryption processing component 260 may decrypt the ECM to obtain somenumber of control words. In some embodiments, from each ECM received bydecryption processing component 260, two control words are obtained. Insome embodiments, when decryption processing component 260 receives anECM, it compares the ECM to the previously received ECM. If the two ECMsmatch, the second ECM is not decrypted because the same control wordswould be obtained. In other embodiments, each ECM received by decryptionprocessing component 260 is decrypted; however, if a second ECM matchesa first ECM, the outputted control words will match; thus, effectively,the second ECM does not affect the control words output by decryptionprocessing component 260. Decryption processing component 260 may bepermanently part of television receiver 200 or may be configured to beinserted and removed from television receiver 200.

Tuning management processor 210-2 may be in communication with tuners215 and control processor 210-1. Tuning management processor 210-2 maybe configured to receive commands from control processor 210-1. Suchcommands may indicate when to start/stop recording a television channeland/or when to start/stop causing a television channel to be output to atelevision. Tuning management processor 210-2 may control tuners 215.Tuning management processor 210-2 may provide commands to tuners 215that instruct the tuners which satellite, transponder, and/or frequencyto tune to. From tuners 215, tuning management processor 210-2 mayreceive transponder streams of packetized data. As previously detailed,some or all of these packets may include a PID that identifies thecontent of the packet.

Tuning management processor 210-2 may be configured to create one ormore PID filters 255 that sort packets received from tuners 215 based onthe PIDs. When a tuner is initially tuned to a particular frequency(e.g., to a particular transponder of a satellite), a PID filter may becreated based on the PMT data. The PID filter created, based on the PMTdata packets, may be known because it is stored as part of NIT 240 oranother table, such as a program association table (PAT). From the PMTdata packets, PMT may be constructed by tuning management processor210-2.

PID filters 255 may be configured to filter data packets based on PIDs.In some embodiments, PID filters 255 are created and executed by tuningmanagement processor 210-2. For each television channel to be output forpresentation or recorded, a separate PID filter may be configured. Inother embodiments, separate hardware may be used to create and executesuch PID filters. Depending on a television channel selected forrecording/viewing, a PID filter may be created to filter the video andaudio packets associated with the television channel (based on the PIDassignments present in PMT 257). For example, if a transponder datastream includes multiple television channels, data packets correspondingto a television channel that is not desired to be stored or displayed bythe user may be ignored by PID filters 255. As such, only data packetscorresponding to the one or more television channels desired to bestored and/or displayed may be filtered and passed to eitherdescrambling engine 265 or decryption processing component 260; otherdata packets may be ignored. For each television channel, a stream ofvideo packets, a stream of audio packets (one or both of the audioprograms) and/or a stream of ECM packets may be present, each streamidentified by a PID. In some embodiments, a common ECM stream may beused for multiple television channels. Additional data packetscorresponding to other information, such as updates to NIT 240, may beappropriately routed by PID filters 255. At a given time, one ormultiple PID filters may be executed by tuning management processor210-2.

Descrambling engine 265 may use the control words output by decryptionprocessing component 260 in order to descramble video and/or audiocorresponding to television channels for storage and/or presentation.Video and/or audio data contained in the transponder data streamreceived by tuners 215 may be scrambled. Video and/or audio data may bedescrambled by descrambling engine 265 using a particular control word.Which control word output by decryption processing component 260 to beused for successful descrambling may be indicated by a scramble controlidentifier present within the data packet containing the scrambled videoor audio. Descrambled video and/or audio may be output by descramblingengine 265 to storage medium 225 for storage (in DVR database 245)and/or to decoder module 233 for output to a television or otherpresentation equipment via television interface 235. Video and/or audiothat is to be stored to DVR database 245 may be re-encrypted and/orre-scrambled using a different encryption and/or scrambling method andkeys. Such re-encryption and/or scrambling may be performed by controlprocessors 210-1 or some other processing component.

It should be understood that storage medium 225 may include multipleforms of processor-readable storage devices. For example, thumbnail andmetadata buffer 140 may be stored using an on-processor buffer or randomaccess memory, while thumbnail datastore 142, metadata datastore 144,and DVR database 245 may be stored using a hard drive or solid-statedrive.

For simplicity, television receiver 200 of FIG. 2 has been reduced to ablock diagram; commonly known parts, such as a power supply, have beenomitted. Further, some routing between the various modules of televisionreceiver 200 has been illustrated. Such illustrations are for exemplarypurposes only. The state of two modules not being directly or indirectlyconnected does not indicate the modules cannot communicate. Rather,connections between modules of the television receiver 200 are intendedonly to indicate possible common data routing. It should be understoodthat the modules of television receiver 200 may be combined into a fewernumber of modules or divided into a greater number of modules. Further,the components of television receiver 200 may be part of another device,such as built into a television. Television receiver 200 may include oneor more instances of various computerized components, such ascommunication buses, processors, storage mediums, interfaces, powersupplies, that have been omitted for simplicity.

FIG. 3 illustrates an embodiment 300 of an interface that allows forthumbnail-based navigation. The thumbnail-based navigation interface ofFIG. 3 can be created using television receiver 200 or some other formof system or device that has system 100 of FIG. 1 incorporated. Inembodiment 300, video content 310 is currently being output bytelevision 301. Video content 310 may be video content that is receivedlive and is being output for presentation soon after being received bythe television receiver. In embodiment 300, video content 310corresponds to current playback location 325 of time shift buffer visualrepresentation 330 on scrub bar 340. Live video, as received, wouldcorrespond to playback location 331. By providing user input, such as bypressing a rewind button or scrolling to the left, a user may movevisual indication 321 along scrub bar 340 to a position within timeshift buffer visual representation 330. Based on the location of visualindication 321, a corresponding thumbnail image may be retrieved from athumbnail datastore, such as thumbnail datastore 142 of FIG. 1. Theretrieved thumbnail may be presented in thumbnail display region 320. Ascan be seen in the example of embodiment 300, at the earlier locationcorresponding to visual indication 321, the video content features apair of horses as indicated in thumbnail display region 320. If thelocation of visual indication 321 is changed, a different thumbnail maybe retrieved, which would correspond to a different thumbnail image.

The systems, devices, and interfaces of FIGS. 1-3 may be used to performvarious methods. FIG. 4 illustrates an embodiment of method 400 forgenerating live thumbnails. Method 400 may be performed using system100. Method 400 may be performed using system 100 as incorporated aspart of television receiver 200. Each step of method 400 may beperformed using system 100 of FIG. 1. At block 410, a stream of videocontent may be received. A user may have provided input indicatingwhether the video content is to be output for viewing live, is to berecorded to a non-transitory computer readable medium for viewing at alater time, or both. In some embodiments, the stream of video content isreceived via a tuner, such as a tuner that receives content from asatellite via a satellite antenna. In some embodiments, the stream ofvideo content may be received via a packet-based network, such as theInternet. In other embodiments, a cable based network or some other formof wired or wireless communication may be possible to enable thetelevision receiver to receive the stream of video content at block 410.The video content being received at block 410 may continue to occurthroughout method 400.

At block 420, the received video content may be decrypted and/ordescrambled by the television receiver. In some embodiments, such asthose using a set top box, a decryption key may be used to decrypt anencrypted message. From the encrypted message, a descrambling key may beobtained. The scrambling key may then be used to descramble the receivedvideo content. In other embodiments, some other arrangement may be usedto decrypt, descramble, or decode the received video content. In someembodiments, the video content may not be encrypted or scrambled.

At block 430, a determination may be made by a thumbnail generationprocess being executed by one or more processors of the televisionreceiver as to whether a predefined time period has elapsed since a lastthumbnail was generated for the piece of video content. The thumbnailgeneration process may be in a sleep mode while block 430 is beingperformed. This predefined time period may be set by a televisionservice provider via a configuration setting of the television receiver.Therefore, the predefined time period may be adjusted by the televisionservice provider. The greater the predefined time period, the fewer thenumber of thumbnails generated and the less amount of processing needingto be performed by the one or more processors. The smaller thepredefined time period, the greater the number of thumbnails generatedand the greater the amount of processing needing to be formed by the oneor more processors to create the thumbnails.

In some embodiments, the amount of time between when thumbnails aregenerated may be dynamically varied based on the processing load on theone or more processors of the television receiver. Therefore, if the oneor more processors are currently being significantly utilized, theamount of time between generation of thumbnails may be increased (todecrease the amount of processing load due to thumbnail generation).

The amount of time may additionally or alternatively be adjusted basedon the type of display that will be used to output the content forpresentation. For example, on a small display, having fewer thumbnails(which may be created using a lower resolution) may be sufficient fornavigation. A smaller number of thumbnails may be sufficient due to thesize of the scrub bar (due to the size of the display) and the inabilityto do highly precise movements with a finger on a small scrub bar.Therefore, the size and/or resolution of a display that will be used foroutput may be taken into account to determine the amount of time and/orresolution for thumbnails.

Additionally or alternatively, thumbnail creation may be offloaded to acloud-based server, such as a server operated by a television serviceprovider. An I-frame of the received live video may be sent to thecloud-based server, such as via an IP-based network (which may not bethe same network through which the content was received, such as in asatellite-based television distribution network). The cloud-based servermay then perform the frame decoding, resizing, then re-encode theresized image as a JPEG image (or other format). This arrangement mayincrease network traffic of the television receiver, but may decreasethe amount of processing performed locally by the one or more processorsof the television receiver. Cloud-based thumbnail generation may betriggered by the one or more processors experiencing at least athreshold level of processing load.

If block 430 is evaluated in the negative, the thumbnail generationprocess may remain in a sleep mode. While in the sleep mode, the onlyfunction being performed by the thumbnail generation process may be torepeatedly determine if the predefined time period has elapsed since thelast generated thumbnail. Therefore, if block 430 is evaluated in thenegative, method 400 may proceed to block 490.

If block 430 is evaluated in the positive, method 400 may proceed toblock 440. At block 440, the thumbnail process may be woken from a sleepstate and set to an active state or mode. When set to an active state,the thumbnail generation process may be triggered to create a thumbnailimage based on video content being received. At block 450, the thumbnailgeneration process may monitor the stream of video content beingreceived for the next I-frame to be received. The thumbnail generationprocess may monitor the output of the component that is decryptingand/or descrambling the received video content for the I-frame. Forexample, referring to television receiver 200, thumbnail generationengine 130 may monitor an output of descrambling engine 265 for the nextI-frame.

Based on the located I-frame, a thumbnail image may be generated atblock 460. The thumbnail image may be based on the I-frame and may be ofa reduced resolution from the I-frame. Along with generating thethumbnail image, at block 460, metadata may be created, such as atimestamp that indicates a time to which the thumbnail imagecorresponds. At block 470, the thumbnail and the associated metadata maybe stored. Initially, the thumbnail in the associated metadata may bestored to a buffer, such as in random access memory (RAM). After acertain number of sets of thumbnails and metadata have been stored tothe buffer, a batch write process may be performed to write thethumbnails and the metadata to a long-term processor readable storagemedium, such as a hard drive or solid state drive. In some embodiments,rather than being based on a certain number of sets of thumbnails andmetadata having been stored to the buffer, after a predefined period oftime, such as 30 minutes, the sets of metadata and thumbnails may bewritten to the long-term processor readable storage medium. In someembodiments, other events may trigger the batch write, such as: the endof the stream of video content being received, a user command beingreceived to end recording, or a power off command.

At block 480, the thumbnail generation process may be set to a sleepmode in response to the thumbnail having been generated and stored atblock 460 and 470. Since a thumbnail image was just generated, it can beexpected that at least several seconds will elapse before block 430determines that the predefined time period has elapsed. In someembodiments, the predefined time period may be set to five seconds. Inother embodiments, greater or shorter predefined time periods may bepossible.

At block 490, the video content being received at block 410 anddecrypted and/or descrambled at block 420 may be: output forpresentation and/or stored. If output for presentation, the descrambledand/or decrypted content may be output to a presentation device, such asa display screen, incorporated as part of the television receiverdevice. For instance, a display of a tablet computer may be used. Inother embodiments, an external display may be used, such as a televisionor monitor connected with the television receiver. Additionally oralternatively, the content may be stored for later viewing. The contentmay be stored as part of a time-shift buffer, such as if a user iscurrently viewing an earlier portion of the content being received. Thecontent may also be stored to a DVR database, such as if the videocontent was scheduled to be recorded based on a timer set by a user orby the television service provider. In some embodiments, if the videocontent is to be stored temporarily, the video content may be scrambledand/or encrypted. If encrypted and/or scrambled, a different algorithmand/or a different scrambling or encryption key may be used than wasused for decryption and/or descrambling at block 420.

FIG. 5 illustrates an embodiment of a method 500 for using generatedlive thumbnails for navigation in video content. Method 500 may beperformed using one or more thumbnails that were generated according tomethod 400 of FIG. 4. Each block of method 500 may be performed using atelevision receiver, such as the television receiver of FIG. 2. In otherembodiments, a television receiver that is an application being executedby a computerized device, such as a tablet computer or smart phone, mayperform method 500.

At block 510, a stream of video content may be received. A user may haveprovided input indicating whether the video content is to be output forviewing live, is to be recorded to a non-transitory computer readablemedium for viewing at a later time, or both. In some embodiments, thestream of video content is received via a tuner, such as a tuner thatreceives content from a satellite via a satellite antenna. In someembodiments, the stream of video content may be received via apacket-based network, such as the Internet. In other embodiments, acable based network or some other form of wired or wirelesscommunication may be possible to enable the television receiver toreceive the stream of video content at block 510. The video contentbeing received at block 510 may continue to occur throughout method 500.

At block 520, input may be received that triggers presentation of anavigation interface. For instance, user may press a button on a remotecontrol that is being used as a user input device for the televisionreceiver. Alternatively, a user may tap the screen to trigger thepresentation of the navigation interface. At block 525, a navigationinterface may be caused to be presented by the television receiver. Thenavigation interface may be similar to the navigation interface of FIG.3. At block 530, input may be received that is indicative of anavigation location within the video content that has been (or is being)received. The navigation interface may include a scrub bar thatindicates a portion of the content that is available for navigation dueto it having been previously recorded, such as using DVR functionalityor a time-shift buffer. The input received at block 530 may involvemoving forward or backward within the piece of content from a currentplayback position.

In response to a position within the video content selected at block530, the television receiver may access a metadata datastore to identifya corresponding thumbnail at block 540. Using the metadata datastore,the television receiver may determine an identifier of a thumbnail thatcorresponds to a particular time within the piece of content. Using theidentifier, a thumbnail datastore may be accessed to retrieve thecorresponding thumbnail at block 545.

At block 550, the thumbnail retrieved at block 545 may be presented inrelation to the current navigation location. A user may then continue tonavigate to another location or may select the current location forplayback.

The methods, systems, and devices discussed above are examples. Variousconfigurations may omit, substitute, or add various procedures orcomponents as appropriate. For instance, in alternative configurations,the methods may be performed in an order different from that described,and/or various stages may be added, omitted, and/or combined. Also,features described with respect to certain configurations may becombined in various other configurations. Different aspects and elementsof the configurations may be combined in a similar manner. Also,technology evolves and, thus, many of the elements are examples and donot limit the scope of the disclosure or claims.

Specific details are given in the description to provide a thoroughunderstanding of example configurations (including implementations).However, configurations may be practiced without these specific details.For example, well-known circuits, processes, algorithms, structures, andtechniques have been shown without unnecessary detail in order to avoidobscuring the configurations. This description provides exampleconfigurations only, and does not limit the scope, applicability, orconfigurations of the claims. Rather, the preceding description of theconfigurations will provide those skilled in the art with an enablingdescription for implementing described techniques. Various changes maybe made in the function and arrangement of elements without departingfrom the spirit or scope of the disclosure.

Also, configurations may be described as a process which is depicted asa flow diagram or block diagram. Although each may describe theoperations as a sequential process, many of the operations can beperformed in parallel or concurrently. In addition, the order of theoperations may be rearranged. A process may have additional steps notincluded in the figure. Furthermore, examples of the methods may beimplemented by hardware, software, firmware, middleware, microcode,hardware description languages, or any combination thereof. Whenimplemented in software, firmware, middleware, or microcode, the programcode or code segments to perform the necessary tasks may be stored in anon-transitory computer-readable medium such as a storage medium.Processors may perform the described tasks.

Having described several example configurations, various modifications,alternative constructions, and equivalents may be used without departingfrom the spirit of the disclosure. For example, the above elements maybe components of a larger system, wherein other rules may takeprecedence over or otherwise modify the application of the invention.Also, a number of steps may be undertaken before, during, or after theabove elements are considered.

What is claimed is:
 1. A method for generating thumbnail images forvideo content navigation, the method comprising: receiving, by atelevision receiver, video content; while the video content is beingreceived: waking, by one or more processors of the television receiver,a thumbnail generation process from a sleep state; monitoring, by thethumbnail generation process being executed by the one or moreprocessors of the television receiver, the received video content for anI-frame; creating, by the thumbnail generation process being executed bythe one or more processors of the television receiver, a thumbnail imagethat is mapped to a timestamp; storing, by the thumbnail generationprocess being executed by the one or more processors of the televisionreceiver, the thumbnail image mapped to the timestamp; and in responseto storing the thumbnail image, causing the thumbnail generation processto enter the sleep state.
 2. The method for generating thumbnail imagesfor video content navigation of claim 1, wherein the thumbnailgeneration process is woken from the sleep state based on determining apredefined time period has expired.
 3. The method for generatingthumbnail images for video content navigation of claim 1, wherein thethumbnail generation process is woken from the sleep state based on acurrent processing load of the one or more processors.
 4. The method forgenerating thumbnail images for video content navigation of claim 1,wherein receiving the video content comprises: decrypting, by thetelevision receiver, a control message to obtain a descrambling key;receiving, by the television receiver, via a tuner, scrambled videocontent; and descrambling, by the television receiver, the scrambledvideo content using the descrambling key, wherein the thumbnail image iscreated after the scrambled video content is descrambled.
 5. The methodfor generating thumbnail images for video content navigation of claim 4,further comprising: after descrambling the scrambled video content usingthe descrambling key and creating the thumbnail image, encrypting thevideo content, wherein the thumbnail is created before the descrambledvideo content is encrypted; and storing the encrypted video content to aprocessor-readable storage medium of the television receiver.
 6. Themethod for generating thumbnail images for video content navigation ofclaim 4, further comprising: storing, by the television receiver, thereceived video content to a time shift buffer stored on a non-transitorycomputer-readable medium.
 7. The method for generating thumbnail imagesfor video content navigation of claim 2, wherein, during the sleepstate, the thumbnail generation process only monitors whether thepredefined time period has elapsed since a previous thumbnail wasgenerated.
 8. The method for generating thumbnail images for videocontent navigation of claim 1, wherein storing the thumbnail imagemapped to the timestamp comprises: creating a first file that stores aplurality of thumbnail images, the plurality of thumbnail imagescomprising the thumbnail image; and creating a second file that linkseach of the plurality of thumbnail images with a timestamp of aplurality of timestamps.
 9. The method for generating thumbnail imagesfor video content navigation of claim 1, further comprising, while thevideo content is being received: outputting, by the television receiver,for presentation, a video content navigation interface, wherein thevideo content navigation interface comprises: a scrub bar; and thethumbnail image, wherein a time mapped to the timestamp of the thumbnailimage is currently selected.
 10. The method for generating thumbnailimages for video content navigation of claim 9, wherein outputting thevideo content navigation interface further comprises: receiving userinput selecting a location on the scrub bar; and presenting a secondthumbnail image that is mapped to a timestamp corresponding to thelocation on the scrub bar.
 11. The method for generating thumbnailimages for video content navigation of claim 1, wherein the thumbnailimage is a reduced resolution version of the I-frame.
 12. A televisionreceiver, comprising: one or more processors; a memory communicativelycoupled with and readable by the one or more processors and havingstored therein processor-readable instructions which, when executed bythe one or more processors, cause the one or more processors to:receiving video content; while the video content is being received:based on a predefined time period expiring, activate a thumbnailgeneration process from a sleep state; monitor the received videocontent for an I-frame by the activated thumbnail generation process;create a thumbnail image that is mapped to a timestamp by the activatedthumbnail generation process; cause the thumbnail image mapped to thetimestamp to be stored; and cause the thumbnail generation process toenter the sleep state for the predefined time period in response tostoring the thumbnail image.
 13. The television receiver of claim 12,wherein the processor-readable instructions that, when executed, causethe one or more processors to receive the video content compriseprocessor-readable instructions which, when executed, cause the one ormore processors to: decrypt a control message to obtain a descramblingkey; receive scrambled video content; and descramble the scrambled videocontent using the descrambling key, wherein the thumbnail image iscreated after the scrambled video content is descrambled.
 14. Thetelevision receiver of claim 13, wherein the processor-readableinstructions, when executed, further cause the one or more processorsto: encrypt the video content after descrambling the scrambled videocontent using the descrambling key and creating the thumbnail image,wherein the thumbnail is created before the descrambled video content isencrypted; and cause the encrypted video content to be stored to aprocessor-readable storage medium of the television receiver.
 15. Thetelevision receiver of claim 13, wherein the processor-readableinstructions, when executed, further cause the one or more processorsto: cause the received video content to store to a time shift bufferstored on a non-transitory computer-readable medium.
 16. The televisionreceiver of claim 12, wherein, during the sleep state, the thumbnailgeneration process only monitors whether the predefined time period haselapsed since a previous thumbnail was generated.
 17. The televisionreceiver of claim 12, wherein the processor-readable instructions that,when executed, cause the one or more processors to cause the thumbnailimage mapped to the timestamp to be stored comprise processor-readableinstructions which, when executed, cause the one or more processors to:create a first file that stores a plurality of thumbnail images, theplurality of thumbnail images comprising the thumbnail image; and createa second file that links each of the plurality of thumbnail images witha timestamp of a plurality of timestamps.
 18. The television receiver ofclaim 12, wherein the processor-readable instructions, when executed,further cause the one or more processors to, while the video content isbeing received: cause the television receiver to output for presentationa video content navigation interface, wherein the video contentnavigation interface comprises: a scrub bar; and the thumbnail image,wherein a time mapped to the timestamp of the thumbnail image iscurrently selected.
 19. The television receiver of claim 18, wherein theprocessor-readable instructions that, when executed, cause the one ormore processors to output the video content navigation interfacecomprise processor-readable instructions which, when executed, cause theone or more processors to: receive user input selecting a location onthe scrub bar; and cause a second thumbnail image to be presented thatis mapped to a timestamp corresponding to the location on the scrub bar.20. The television receiver of claim 12, wherein the thumbnail image isa reduced resolution version of the I-frame.